JP2904357B2 - Method for producing surface-coated aluminum alloy - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a surface-coated aluminum alloy that is optimal for wear-resistant parts that require wear resistance and welding resistance.

(Prior Art) Al alloys are used as lightweight structural materials in automobile parts and other main structural materials related to space aircraft, various mechanical parts, dies and the like. However, Al alloys have the drawback that wear resistance is significantly inferior to steel materials. For this reason, there is a limit in applying the Al alloy to a member that is subjected to severe wear or friction. Ideally, a steel material is used where an Al alloy should be used. A surface hardening method is the most effective method for improving the wear resistance of an Al alloy.

Various plating methods such as hard alumite treatment, Ni plating, and Cr plating have been put into practical use for the surface hardening treatment of Al alloys.
Hardness is about Hv300 by alumite treatment and Hv6 by plating.
00 to 700, and the film thickness is at most several tens of μm. As the demand for Al alloys, which are lightweight materials, grows, the surface hardening process with a thickness of several mm, which is durable against large impacts and high surface pressures, and with a thickness of several μm to maintain dimensional accuracy Processing showing high hardness has been required.

(Problems to be Solved by the Invention) For parts requiring dimensional accuracy, such as molds and mechanical parts, a surface treatment that shows high hardness with a thickness of several micrometers while maintaining the hardness and strength of the Al alloy is required. Required. The Al alloy is usually subjected to age hardening at 120 ° C. to 170 ° C., and at a temperature of 200 ° C. or more, the hardness and strength are reduced. For surface hardening of precision parts made of Al alloy, it is important to treat at a low temperature of 200 ° C or less. To achieve these goals,
It is considered that the ion plating method capable of forming a ceramic hard coating at a relatively low temperature is optimal, but the radiation from the evaporation source and the kinetic energy of the ions increase the substrate temperature to 200 ° C. or more. By reducing the film forming speed
Although it is possible to form a film at a temperature of 200 ° C. or lower, there is a problem that the film quality is remarkably deteriorated and the wear resistance is reduced.

Therefore, an object of the present invention is to coat a hard coating on an Al alloy at a temperature of 200 ° C. or less using an ion plating method,
An object of the present invention is to provide a method for producing a surface-coated Al alloy having excellent wear resistance.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides an aluminum plating method using an ion source of chromium metal as an evaporation source, a nitrogen gas, an ammonia gas, or a mixed gas thereof as a reaction gas. In the method of forming a nitride film on an alloy, a bias voltage of 0 to −50 V is applied to the aluminum alloy, the pressure of the reaction gas is increased to 10 × 10 ⁻³ Torr or more, and the temperature during film formation is set to 200 ° C. A method for producing a surface-coated aluminum alloy, which is maintained as follows, is employed.

When a production method under such conditions is used, it is possible to form a film having excellent wear resistance composed of a CrN single-phase precipitated phase while maintaining the hardness and strength of the Al alloy as a substrate. The thickness of such a coating is preferably 0.2-20 μm
m.

(Action) CrN is a substance having high oxidation resistance, and the coating formed by this has an excellent effect to prevent embrittlement and wear due to oxidation at high temperature, but it has resistance to other causes than oxidation. It is not enough in terms of wear. The reason is that the precipitation of Cr ₂ N or Cr in the CrN film reduces the strength, and the present inventor has shown that if the precipitation of Cr ₂ N or Cr is suppressed, extremely good wear resistance is exhibited. In particular, it was found that when the maximum diffraction intensity attributed to Cr ₂ N or Cr by X-ray diffraction measurement was 5% or more of the maximum diffraction intensity attributed to CrN, the coating strength was significantly reduced. . For this reason, the present inventor has achieved a film forming method for suppressing precipitation of Cr ₂ N and Cr while preventing a decrease in hardness and strength of the film, and the film forming conditions will be described below. .

When the pressure of the reaction gas is less than 10 × 10 ⁻³ Torr and the bias voltage is −100 V to −800 V, the precipitation of Cr ₂ N in the CrN film is observed, and in this case, CrN and Cr ₂ N
In a mixed phase state. When the reaction gas pressure is less than 10 × 10 ⁻³ Torr and the bias voltage is less than −100 V, Cr precipitates and becomes a mixed phase of CrN and Cr. On the other hand, when the reaction gas pressure is set to 10 × 10 ⁻³ Torr or more, the phase becomes CrN single phase, and the wear resistance is remarkably improved.
Is exceeded, the substrate temperature becomes 200 ° C. or higher. When an Al alloy is used as the substrate, if the film forming temperature exceeds 200 ° C., the hardness and strength are reduced. Therefore, the film forming conditions are summarized as follows. The bias voltage is in the range of 0 to −50 V, and the reaction gas pressure must be 10 × 10 ⁻³ Torr or more.

Preferably, the film thickness is in the range of 0.2 to 20 μm. In other words, if the film thickness is less than 0.2 μm, sufficient wear resistance is not secured because it is too thin, and if the film thickness exceeds 20 μm, cracks are liable to occur due to residual compressive stress in the CrN film. Abrasion is deteriorated.

In the method of the present invention, by setting such film forming conditions, the precipitation of Cr ₂ N or Cr in the CrN film can be controlled, and the film can be formed at 200 ° C. or lower.
Therefore, the coated Al alloy obtained by the method of the present invention has significantly improved wear resistance while maintaining the properties of the Al alloy itself.

As a method of evaporating metal chromium, any of resistance heating, an electron gun, etc. may be used as a method of evaporating metal chromium, and an arc discharge, a glow discharge, a high frequency discharge, etc. may be used as a method of ionizing the evaporated metal chromium. Alternatively, ammonia gas or a mixed gas thereof can be selected.

 Hereinafter, the present invention will be described in detail with reference to the present invention.

Example 1 As a device for carrying out the method of the present invention, a vacuum arc discharge type ion plating device schematically shown in FIG. 1 was used. As the substrate 14 to be coated, a JISA7075P Al alloy was used. After washing this Al alloy with an organic solvent, it was set on a turntable 12 in a vacuum reactor 10 and the pressure in the vacuum reactor was adjusted to 1 × 10 by a vacuum pump (not shown) connected through a port 20. ^{After evacuating to -5} Torr or more, cleaning by Cr ion bombardment and heating were performed to start formation of a CrN film. Metal evaporation source 16 to be coated
Cr is used, but the film formation conditions at this time are such that only nitrogen is introduced as a reaction gas through the reaction gas supply port 18 and the pressure is reduced.
70 × 10 ^-3 Torr. By passing a current of 50 A through the evaporation source 16, Cr ions are released from the Cr target (evaporation source) 16 by vacuum discharge.
A bias voltage of V was applied. Under these conditions, Al
CrN was generated on the alloy surface, and a film having a thickness of 5 μm was obtained by a film forming reaction for about 2 hours. During film formation, temperature is 190 ℃
Met. As a result of X-ray diffraction measurement, the precipitated phase was a single phase of CrN.

ASTM D-
The Falex abrasion test specified in 2714-68 was performed. The test conditions were as follows, and the results were as shown in Table 1 of the attached document.

Lubricant No lubrication in air Rotation speed 60 rpm Load 4.5 kg Test time 10 minutes Material A7075P As is clear from Table 1, the wear width was 1.7 mm, and good results were obtained.

Example 2 A film was formed under the same conditions as in Example 1 except that the pressure of the nitrogen gas in the reaction tank was set to 25 × 10 ⁻³ Torr. The temperature during film formation is
190 ° C. According to the X-ray diffraction results of the formed film, C
Precipitation of rN single phase was observed. When a Falex wear test was performed on the obtained Al alloy, as shown in Table 1, the wear width was 1.9 mm, and good results were obtained.

Comparative Example 1 A film was formed under the same film forming conditions as in Example 1 except that the pressure of the nitrogen gas in the reaction tank was set to 5 × 10 ⁻³ Torr and the bias voltage was set to −200 V. The temperature during the film formation was 320 ° C., and according to the X-ray diffraction result of the formed film, precipitation of CrN and Cr ₂ N was recognized. A Falex wear test was performed on the obtained Al alloy. As shown in Table 1, the wear width was 3.5 mm, and the performance was inferior.

Comparative Example 2 A CrN film was formed under exactly the same conditions as in the example except that the bias voltage was set to -25 V and the nitrogen gas pressure was set to 5 × 10 ⁻³ Torr. According to the result of X-ray diffraction measurement of the coating in this case, precipitation of CrN and Cr was recognized. A Falex wear test was performed on the obtained Al alloy. As shown in Table 1, the wear width was 2.6 mm, and the performance was inferior.

Comparative Example 3 A CrN film was formed under exactly the same conditions as in Example 1 except that the bias voltage was set to -200 V and the nitrogen gas pressure was set to 30 × 10 ⁻³ Torr. According to the result of the X-ray diffraction measurement of the coating in this case, it was a CrN single phase. However, the hardness of the Al alloy, which was Hv170 before the PVD treatment, was reduced to Hv140. Al obtained
When a Falex wear test was performed on the alloy, as shown in Table 1, the wear width was 3.1 mm, and the performance was inferior.

(Effects of the Invention) As described above in detail, according to the present invention, it is possible to perform surface treatment hardening without reducing the hardness and strength of an Al alloy, and to significantly improve the wear resistance of an Al alloy member. Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a vacuum arc discharge type ion plating apparatus for carrying out the method of the present invention. 10… Reaction tank, 12… Turntable, 14… Substrate, 16 …… Target (evaporation source).

Claims (1)

(57) [Claims] 1. A method for forming a nitride film on an aluminum alloy by ion plating using metal chromium as an evaporation source and nitrogen gas, ammonia gas or a mixed gas thereof as a reaction gas. A bias voltage of ~ -50V is applied, the pressure of the above reaction gas is increased to 10 × 10 ^-3 Torr or more, and the temperature during film formation is set to 200 ° C.
A method for producing a surface-coated aluminum alloy, which is maintained as follows.